Orange Mound Spring is one of the several hot springs in Yellowstone National Park. The name comes from its dark orange appearance caused by orange cyanobacteria living on the travertine, the rock that it is made of. The Orange Mound Spring is part of the Mammoth Hot Springs area of the park. The Orange Mound Spring is arguably most notable for its prominence above the ground, compared to the rest of the Mammoth Hot Springs, which are mostly flat and leveled terraces. It was named by early Yellowstone assistant superintendent and guide, G.L. Henderson.